Hydrogels, based on polysaccharides such as chitosan have found various applications as drug delivery carriers. Three different preparations of pH sensitive chitosan/polyvinyl alcohol hydrogels containing inclusion compounds of thyme oil with methyl-β-, hydroxypropyl-βand γ-cyclodextrin were developed by using a controlled, bio-compatible and low cost method based on freeze–thaw cycling. The structures and morphology of the hydrogels were characterized by FTIR, optical and scanning electron microscopy. Stable hydrogels of chitosan and polyvinyl alcohol had good mechanical properties and swelling ratios. The water vapor transmission rates of the hydrogels were all in the range of an ideal wound dressing. Encapsulation and release of thyme oil-cyclodextrin inclusion compounds (TM-CDICs) in the hydrogels were detected and followed by UV spectroscopy and different mathematical models were applied for evaluating the drug release mechanisms. Hydrogels loaded with TM-CD-ICs had slower and more controlled drug release. The antibacterial activity of the samples was studied by counting the number of surviving both gram-negative and gram-positive bacteria in a broth medium and the results showed antibacterial activity of all prepared hydrogels, especially those containing TM-γCD-ICs. The MTT assay indicated more cell viability of TM-γCD-ICs hydrogels in comparison with that of containing βcyclodextrin inclusion compounds (TM-βCD-ICs hydrogels). Cell attachment study showed great biocompatibility of TM-γCD-ICs hydrogels. Finally, the modified hydrogels can be used in different biomedical applications, such as wound dressings for improving the wound healing process and in drug delivery systems.
